Automotive vehicle temperature control systems known in the art typically use ambient temperature sensors and sun load sensors to obtain information on exterior air temperature and solar energy load. The sensors typically are located at various locations in the vehicle. The information gathered from the sensors is used in a logic control system to establish airflow data and outlet temperature for the temperature control system in the vehicle passenger compartment.
The outside ambient air temperature sensor must be strategically placed so that it is positioned away from heat sources, such as the engine of the vehicle. A common location for the ambient temperature sensor is behind the forward radiator grille. This provides fair performance at high vehicle speeds but rather poor performance at lower vehicle speeds, especially if the vehicle is traveling in the direction of surface winds.
A typical location for a sun load sensor usually is in the upper vehicle dash surface where it may be subjected to shadows. It also, when so positioned, has poor directional sensitivity. That is, the sensitivity of the sun load sensor is variable depending upon the sun angle, which varies seasonally as well as hourly.
U.S. Pat No. 5,832,990, filed Nov. 30, 1995, discloses a temperature control system that takes into account airflow, as well as interior temperature, outlet temperature of the system and general comfort parameters while managing the total heat flux. It uses thermodynamic interaction of the comfort parameters, the interior temperature, the outlet temperature and airflow, as well as other control variables, in accordance with a control logic. As in the case of the prior art temperature control systems, the control system of the co-pending application requires a solar load sensor and an ambient temperature sensor.